Transmitter



F. C. BRECKENRIDGE.

TRANSMITTER.

APPLICATION FILED Dic. e, 1919.

Patented May 3, 1921.

' wires which in volume and quality of the,

NTED STABS PATENT OFFICE.

EEANCIS c. BEECKENEIDGE, 0E PROVIDENCE, RHODE ISLAND, ASSIGNoE 'ro AivIERI- CAN 'rIIEEivIoPHoNE COMPANY, 0E EoS'roN, MASSACHUSETTS, A CoRroRAmmN 0F MASSACHUSETTS.

'This in vention relates to the transformation of Sound waves in air into undulatory electrical waves lby causing s'uch sound waves to act upon a fine wire in an electric circuit. Such action changes the resistance of the wire so that electrical waves of considerable amplitude result in the circuit with such rapidity that the component waves required in the transmission ofspeech are transformed with suiiicientfaithfulness vto make possible the transmission of articulate speechff For this purpose I have made a telephone transmitter, using a hot wire or transformed wave is comparable with the carbon transmitter in common use today.

In the development'of my transmitter it :is desirable to subject the current-varying member or members (i. e.,-the wire or wires of my device) to the greatest possible variations of air pressure, in order to produce the desired clearness of articulation and to have all portions ofthe Surface of the vwire in a homogeneous thermo-dynamic state at any linstant of time. It is this feature of my invention which I believe to' be a distinct advance in the art. Such a device as I de` scribe hereafter 'is an improvement overl other. forms of transmitter in that there is no poor contact in the circuit as is the case' in all microphones. Myv transmitter is in consequence not subject to disturbing effects such as packing or burning, which are characteristic of most microphones. I believe this transmitter is especially adapted for use in those cases Where a current.

of very high frequency is varied as in wireless telephony or telegraphy or in multiplex telephony where fcarrier currents of yhigh frequency are used.

In the drawings I have shown various improvements embodying my invention, but I do not mean to limit myself merely to the constructions shown.

f Figure l is a section taken on line lof Fig.

Fig. 2 is a rear elevation of the formI of Specification of Letters' Patent.

Moreover, i

SMITTER.

Patented May 3, i921.

Application iea December 6, 1919. serial No. 34a-oido.

apparatus shown in Fig. 1, the back of the device being removed.

Fig. 3 is a section on line 3 3 of Fig. 4. Fig. is a rear ViewV of the apparatus shown i'n Fig. 3. Figs. 5 and 6 show another form of my invention, these figures being sections taken on lines at right angles to one another.

Figs. 7 and 8 show arrangements ofcircuits suitable for .use with this device. l

The wireused in connection with this apparatus is of as small a gage as can be conveniently handled, and in Figs. 1, 2, 3 and 4 such wire is shown at al. In Figs. 5 and 6 Wires are shown in the form of loops a1. In each case the device is provided with a mouthpiece A of usual character eXcept that the mouthpiece A1 in Fig. 3 is preferably made rectangular. Referring to Fig. l, the mouthpiece A sets into a'plate B having an opening b leading to the wire chamber and carrying lugs b1 projecting rearwardly. U, C are slides running in guideways c and each having connected thereto a screw D passing through one of the lugs b1 and thus serving as a convenient means of adjustment ofthe slot in which the wire t is mounted. The wire a is stretched betweenv screws e, e1, there being a spring f in the wire intermediate the screws e, el .as a means of keeping the wire under tension. These screws e, e1 may serve asbindingposts for the necessary electrical connections. v

' vVl/'hen the wire is heated it expands, and in order to keep it taut and always in parallel relation to the walls of the slot, some means such as the spring 'f is desirable in most cases. The slot g between the members C should best be adjustable in width so that it may meet-the peculiarities of any particular instrument, and this adjustment should be so made that the'wire will pass through the slot at equal distances from the walls thereof. H is a cupshaped back which its over and closes in the rear of the instrument. It serves to forma resonating chamtelephony.

the sides of the slots.

Figs. l and 2. In this case, however, there are a plurality of wires fr, and the slots g are formed between fixed partitions C1. As a means of insuring the proper centering of the wires a` between the partitions Cl, each Wire is connected at one end to a loop a2, the ends of the loop being attached to two adjusting screws e. Either end of the loop may 'thus be lengthened or shortened as may be necessary to center the wire. Each wire ais provided with an elastic or spring j portion f, which in turn is connected to a pin el projecting from the screw e2. Moreover, adjustment at either end is usually sufficient for the purpose. These adjustments may be alike at each end of the wire, or other adjustments may be used if thought best.

In the place of the wire a a thin foil of conducting material may be used, its'thin- In this case the loops are mounted on a support located back of theslot and in the resonance chamber so that the loops project into the slot. The loops may be connected either in series or in multiple depending upon whether the circuit with which thetransmitter is connected is of high or low` resistance.v l

The circuit used with this instrument mayl be of any of those forms commonly used in Figs. 7 and 8 have been used with good effect. In these views the transmitter is lettered T, the receiver R, the battery G and the wire W. In Fig. 8 the battery G is projected across between the wires Wr in series with a split coil VVlof high impedance and low resistance. Other circuits may be used,

Such circuits as are shown inA such as for example the common telephone circuit with induction coil.

In practising this invention there have been used successfully fine platinum Wires of 2.1? microns in diameter made from Wollaston wire. y

It will be obvious to one skilled in the art that other arrangements of wire a may be used and yet come within the scope of the claims of my invention hereinafter made.

That I claim as my invention is l. A current-varying device comprising an extremely thin conductor, an inclosure therefor having a slotted opening, saidv conductor being mounted in said opening, and means whereby variations of air pressure may be directed thereto.

2. In a current-varying device of the kind described, an extremely thin conductor and an inclosure therefor having a slotted opening in which said conductor is mounted, the walls of said inclosure being adjustable wherebythe width of said slot may be adjusted.

3. A current-varying device comprising an extremely thin conductor and an inclosure therefor forming a resonance chamber having a slotted opening said conductor bemg mounted between the walls of said opening, and means for adjusting the size of said resonance chamber.

4. A current-varying device comprising an extremely thin conductor and an inclosure therefor forming a resonance chamber having a slotted opening in which said conductor is mounted, the walls of said inclosure being adjustable whereby the width of said slot may be adjusted, and means for adjusting the size of said resonance chamber.

5. Av current-varying device comprising .an extremely thin conductor, yielding means for keeping it taut, and means for mounting it whereby a maximum variation of air pressure and a substantially homogeneous thermo-dynamic state may exist at every portion of the conductor at any instant of time.

FRANCIS C. BRECKENRIDGE. 

